#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int i = 1;
	double fc = 1;
	double sum = 0;
	for (i = 1; i <= 100; i++)
	{
		if (i % 2 == 1)
			fc = 1;
		else
			fc = -1;

		sum = sum + fc * 1.0 / (double)i;
	}
	printf("sum = %lf \n", sum);
	return 0;
}